EP0197586B1 - Process and devices for producing glass articles - Google Patents

Process and devices for producing glass articles Download PDF

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Publication number
EP0197586B1
EP0197586B1 EP86200488A EP86200488A EP0197586B1 EP 0197586 B1 EP0197586 B1 EP 0197586B1 EP 86200488 A EP86200488 A EP 86200488A EP 86200488 A EP86200488 A EP 86200488A EP 0197586 B1 EP0197586 B1 EP 0197586B1
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EP
European Patent Office
Prior art keywords
ram
mould
sonotrode
plastic mass
extruded
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Expired - Lifetime
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EP86200488A
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German (de)
French (fr)
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EP0197586A2 (en
EP0197586A3 (en
Inventor
Bernard Dr.-Ing. Dipl.-Phys. Lersmacher
Hans Dr. Dipl.-Ing. Lydtin
Pierre Louis Leonard Marie Dr. Derks
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Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Patentverwaltung GmbH
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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Publication of EP0197586A3 publication Critical patent/EP0197586A3/en
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B17/00—Forming molten glass by flowing-out, pushing-out, extruding or drawing downwardly or laterally from forming slits or by overflowing over lips
    • C03B17/04—Forming tubes or rods by drawing from stationary or rotating tools or from forming nozzles
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/12—Other methods of shaping glass by liquid-phase reaction processes
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/0128—Manufacture of preforms for drawing fibres or filaments starting from pulverulent glass
    • C03B37/01282—Manufacture of preforms for drawing fibres or filaments starting from pulverulent glass by pressing or sintering, e.g. hot-pressing
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/0128—Manufacture of preforms for drawing fibres or filaments starting from pulverulent glass
    • C03B37/01288—Manufacture of preforms for drawing fibres or filaments starting from pulverulent glass by extrusion, e.g. of glass powder and binder
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/016—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by a liquid phase reaction process, e.g. through a gel phase
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S65/00—Glass manufacturing
    • Y10S65/90—Drying, dehydration, minimizing oh groups
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S65/00—Glass manufacturing
    • Y10S65/901—Liquid phase reaction process

Definitions

  • the invention relates to a method for producing glass bodies, in which a porous green body is formed from the starting material for the glass body in the form of a plastic mass by extrusion, dried and then cleaned and sintered.
  • the invention further relates to an extrusion press for carrying out such a method with a cylinder provided with an outlet opening and a press ram movable therein.
  • the method mentioned at the outset is particularly suitable for the production of rods and especially also tubes made of quartz glass, e.g. as a starting body for optical waveguides.
  • Optical waveguides are used for a large number of applications, such as for short-range light transmission devices or for long-distance light transmission systems, such as in optical communication systems, and consist predominantly of a glass with a high silicon dioxide content.
  • a method is known in which pulverulent pure or almost pure SiO 2 with a liquid binder in an amount of 1 to 50% by weight and optionally another lubricant which favors the extrusion process in an amount of 0, 1 to 10% by weight, based on the Si0 2 content, is processed to form an extrusion compound and is deformed by means of an extrusion process.
  • suitable liquid binders are organic liquids, such as polyvinyl alcohol, or water.
  • This process corresponds to a procedure of ceramic technology, in which ground powdery raw materials with grain diameters> 1 1 1m are processed with water, binders and lubricants to form highly viscous extrudable masses.
  • Po in Table 11 means the minimum force applied which leads to the exit of the strand, P 1 is the maximum force required for the quantitative extrusion of the strand.
  • the invention has for its object to provide a method of the type mentioned and an extruder of the type mentioned for performing this method, with which it is possible to produce shape-stabilized green body by an extrusion process from starting material for glass body in the form of a relatively highly viscous plastic molding compound with a solid fraction of highly disperse particles.
  • the plastic mass which contains highly dispersed Si0 2 powder as the main constituent and water as the dispersant, is converted into a state of reduced viscosity by utilizing the thixotropy effect by coupling mechanical forces, and is extruded in this state.
  • An extrusion press for carrying out this method is characterized by a press ram with which a sound or ultrasound field can be coupled into a thixotropic plastic mass to be pressed, the press ram preferably comprising an oscillator, an oscillation amplifier coupled to the oscillator via a retaining ring in the oscillation node, and one Sonotrode, by means of which the ultrasonic field can be coupled into the plastic mass to be pressed.
  • the invention is based on the knowledge that the thixotropy effect in the case of plastic compositions with highly disperse Si0 2 powders as the main constituent and H 2 0 as the dispersant can be used to lower the plastic composition initially by the action of mechanical forces, preferably sound or ultrasound To transfer viscosity, which enables an extrusion process that requires a much lower pressure than if a rheologically unchanged mass were to be pressed.
  • a plastic mass is used as the starting material for the glass body, the SiO 2 particles with a diameter in the region from 10 to 500 nm, preferably 15 to 100 nm, with an average particle diameter of 40 nm, wherein a plastic mass with a solid: water weight ratio of 1: 1.5 to 1: 1.8 is used.
  • the plastic mass is brought into a state of reduced viscosity by coupling a sound field with a frequency f in the range from 20 to 200 Hz or by coupling in an ultrasound field with a frequency f in the range from 20 to 50 kHz transferred.
  • a gel-sol conversion occurs in thixotropic systems with any type of mechanical action, such as stirring or shaking.
  • a sound or ultrasonic oscillator is used to liquefy a highly viscous starting mass, the amplitude of which is dimensioned such that the sound or ultrasonic field is coupled into the starting material to be liquefied, this results in a particularly effective dissolution of packing cavities in the starting material.
  • a part of an extrusion press with a press ram 1 is shown.
  • the press ram 1 is made up of several device parts, namely a vibrator 5 operating in the ultrasound range at a frequency f of 20 kHz, a holding ring 7 coupled to the transmission of the contact pressure p in the vibration node 9 and a sonotrode 11 via which the Ultrasonic field can be coupled into the plastic mass 3 to be pressed.
  • the oscillator 5 has on its surface opposite the retaining ring 7 a vibration damping part, which consists of an intermediate piece 17 made of piezoelectric ceramic and a metallic reflector 19.
  • the plastic mass 3 to be pressed is located in a die 13 which has an outlet opening 15.
  • the press die 1 with its sonotrode 11 is slidably fitted into the die 13.
  • the plunger 1 is advanced under a pressure p, the plastic mass 3, with its portion 33 converted into a state of reduced viscosity by the action of ultrasound, enters via the outlet opening 15 into a cylindrical shape 23 arranged in a receptacle 21 (see FIGS. 2a and 2b) .
  • a resilient cylindrical float 25 is slidably fitted, which rests on an air cushion L and which, when the plunger 1 is advanced, moves in the direction of an air outlet opening 27 at the lower end of the closed form 23.
  • a counterforce can be built up in the mold 23, which makes it possible to compensate for the weight of the extruded mass 33 and thereby prevents the molded compact from being torn in the form of a solid cylinder.
  • a core 29 is arranged centrally in the form 23, which enables the pressing of tubular green bodies.
  • the float 25 is hollow-cylindrical and tightly encloses the core 29.
  • FIGS. 2c and 2d show a form 23 which enables the production of long bars (FIG. 2c) and long tubes (FIG. 2d).
  • the sonotrode is designed as a solid cylinder (sonotrode 11) for the production of tubes or as a hollow cylinder (sonotrode 31) for the production of rods.
  • a mass fraction 33 is formed in the mass 3 to be pressed, which has a lower viscosity than the mass 3.
  • the sonotrode 11, 31 is fed at a feed speed ⁇ in the direction of the arrow, the lower-viscosity mass 33 can flow into the space between the wall of the mold 23 and the sonotrode 11.
  • a sonotrode 31 designed as a hollow cylinder is used, which is slidably fitted into the mold 23, the lower-viscosity mass 33 can flow into the interior of the sonotrode 31 at a feed speed ⁇ in the direction of the arrow and it becomes a rod-shaped ger preserved green body.
  • the form 23 is expediently composed of detachable, removable tubular parts which can be removed after the deformed compact has emerged to reduce the wall friction.
  • masses to be pressed were produced, as indicated in Table I. Due to different mixing treatment and relatively long storage under reduced air access (up to 20 days), the masses showed a very strong solidification (hard, crumbling). The masses could not be extruded in a normal extrusion system, but solidified even more.
  • the same masses were then subjected to a sound treatment in the extrusion press according to the invention in accordance with FIG.
  • the cleaned green body was then densely sintered.
  • the glass body produced had a density of 2.20 g / cm 3 and was free of bubbles and streaks.
  • Glasses which are suitable for optical waveguides can also be used with advantage for the production of lamp bulbs for halogen or gas discharge lamps, because these glasses, like the glasses for optical waveguides, must be virtually water-free and have a high silicon dioxide content.

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von Glaskörpern, bei dem aus dem Ausgangsmaterial für den Glaskörper in Form einer plastischen Masse ein poröser Grünkörper durch Strangpressen geformt, getrocknet und anschließend gereinigt und gesintert wird.The invention relates to a method for producing glass bodies, in which a porous green body is formed from the starting material for the glass body in the form of a plastic mass by extrusion, dried and then cleaned and sintered.

Die Erfindung bezieht sich weiter auf eine Strangpresse zur Durchführung eines solchen Verfahrens mit einem mit einer Austrittsöffnung versehenen Zylinder und einem in diesem bewegbaren Preßstempel.The invention further relates to an extrusion press for carrying out such a method with a cylinder provided with an outlet opening and a press ram movable therein.

Das eingangs genannte Verfahren ist insbesondere geeignet zur Herstellung von Stäben und besonders auch Rohren aus Quarzglas, z.B. als Ausgangskörper für optische Wellenleiter.The method mentioned at the outset is particularly suitable for the production of rods and especially also tubes made of quartz glass, e.g. as a starting body for optical waveguides.

Optische Wellenleiter werden für eine Vielzahl von Anwendungszwecken eingesetzt, so für Licht- übertragungseinrichtungen kurzer Distanz oder für Lichtübertragungssysteme großer Distanz, wie bei optischen Kommunikationssystemen, und bestehen überwiegend aus einem Glas mit hohem Siliciumdioxidgehalt.Optical waveguides are used for a large number of applications, such as for short-range light transmission devices or for long-distance light transmission systems, such as in optical communication systems, and consist predominantly of a glass with a high silicon dioxide content.

Aus GB-PS 1 010 702 ist ein Verfahren bekannt, bei welchem pulverförmiges reines oder nahezu reines Si02 mit einem flüssigen Bindemittel in einer Menge von 1 bis 50 Gew.% und gegebenenfalls einem weiteren, den Strangpreßprozeß begünstigenden Gleitmittel in einer Menge von 0,1 bis 10 Gew.%, bezogen auf den Si02-Anteil, zu einer Strangpreßmasse verarbeitet und über einen Strangpreßprozeß verformt wird. Als flüssige Bindemittel kommen z.B. organische Flüssigkeiten, wie Polyvinylalkohol, oder Wasser in Betracht.From GB-PS 1 010 702 a method is known in which pulverulent pure or almost pure SiO 2 with a liquid binder in an amount of 1 to 50% by weight and optionally another lubricant which favors the extrusion process in an amount of 0, 1 to 10% by weight, based on the Si0 2 content, is processed to form an extrusion compound and is deformed by means of an extrusion process. Examples of suitable liquid binders are organic liquids, such as polyvinyl alcohol, or water.

Dieses Verfahren entspricht einer Arbeitsweise der keramischen Technik, bei der aufgemahlene pulverförmige Rohstoffe mit Korndurchmessern > 1 11m mit Wasser, Bindemitteln und Gleitmitteln zu hochviskosen strangpreßfähigen Massen aufbereitet werden.This process corresponds to a procedure of ceramic technology, in which ground powdery raw materials with grain diameters> 1 1 1m are processed with water, binders and lubricants to form highly viscous extrudable masses.

Beim Verarbeiten von hochdispersen Ausgangspulvern mit Korndurchmessern < 1 11m (die durch übliche Mahlprozesse nicht mehr herstellbar sind), wie sie für die Herstellung von Quarzglaskörpern (insbesondere auch für Vorformen von optischen Wellenleitern) eingesetzt werden, entstehen Probleme beim Mischen bzw. Kneten, besonders dann, wenn die Ausgangsmassen einen hohen Anteil an disperser Phase enthalten, da dann eine wesentlich größere Anzahl von Teilchen gleichmäßig verteilt und eine entsprechend große Oberfläche mit den Zusatzstoffen (Binde- und Gleitmittel) gleichmäßig bedeckt werden muß. So liegen beispielsweise die typischen Misch- und Knetzeiten für eine Ausgangsmasse aus hochdispersen Quarzglasteilchen (10 bis 100 nm Teilchendurchmesser) mit 60 Gew.% Si02 und 36 Gew.% Wasser (Rest Zusatzstoffe) bei einer bis drei Stunden. Neben diesem hohen Zeitbedarf für die Homogenisierung einer strangpreßfähigen Ausgangsmasse tritt ein weiteres Problem auf: Die zu verarbeitenden plastischen Massen mit Si02-Glaspulvern als Hauptbestandteil und Wasser als Dispergiermittel erweisen sich als rheologisch äußert komplexe Gebilde, über deren Verhalten im Formgebungsprozeß praktisch keine Voraussage zu machen ist.When processing highly disperse starting powders with grain diameters <1 11m (which can no longer be produced by conventional grinding processes), as are used for the production of quartz glass bodies (especially also for preforming optical waveguides), problems arise during mixing or kneading, especially then If the starting materials contain a high proportion of disperse phase, since then a much larger number of particles must be evenly distributed and a correspondingly large surface must be covered with the additives (binding agents and lubricants). For example, the typical mixing and kneading times for a starting mass of highly dispersed quartz glass particles (10 to 100 nm particle diameter) with 60% by weight SiO 2 and 36% by weight water (rest of additives) are one to three hours. In addition to this high time requirement for the homogenization of an extrudable starting mass, a further problem arises: The plastic masses to be processed with SiO 2 glass powders as the main constituent and water as the dispersing agent prove to be rheologically extremely complex structures, the behavior of which in the shaping process makes practically no prediction is.

Es hat sich gezeigt, daß bereits geringfügige Unterschiede in der Zusammensetzung und Vorbehandlung sowie Lagerung der Massen extrem starke Auswirkungen auf das Verhalten bei der Extrusion haben. Dies sei hier am Beispiel zweier Massen von nahezu identischer Zusammensetzung und Behandlung dargestellt (vergleiche Tabelle I):

Figure imgb0001
It has been shown that even slight differences in the composition and pretreatment and storage of the masses have extremely strong effects on the behavior during extrusion. This is shown here using the example of two masses of almost identical composition and treatment (see Table I):
Figure imgb0001

Trotz dieser nahezu gleichen Zusammensetzung und (bis auf die Knetzeit t) nahezu gleiche Vorbehandlung ergaben sich bei der Extrusion erhebliche Unterschiede. Die in der nachfolgenden Tabelle II angegebenen Daten gelten für die Kaltextrusion je eines Stranges aus den beiden Mischungen von ca. 20 cm Länge und 1,6 cm Durchmesser aus einer Strangpreßvorrichtung, wie sie aus dem Stand der Technik bekannt ist.

Figure imgb0002
Despite this almost the same composition and (apart from the kneading time t) almost the same pretreatment, there were considerable differences in the extrusion. The data given in Table II below apply to the cold extrusion of one strand each from the two mixtures of approximately 20 cm in length and 1.6 cm in diameter from an extrusion device as is known from the prior art.
Figure imgb0002

Po in Tabelle 11 bedeutet die aufgebrachte Minimalkraft, die zum Austritt des Stranges führt, P1 ist die zum quantitativen Auspressen des Stranges erforderliche maximale Kraft.Po in Table 11 means the minimum force applied which leads to the exit of the strand, P 1 is the maximum force required for the quantitative extrusion of the strand.

Während der Extrusion (in der Zeit t=10 s bzw. 20 s) musste die Preßkraft kontinuierlich gesteigert werden.During the extrusion (in the time t = 10 s or 20 s), the pressing force had to be increased continuously.

Dieses stark unterschiedliche Verhalten der beiden Massen deutet darauf hin, daß das Fließ- bzw. Verformungsverhalten demjenigen eines sogenannten strukturviskosen Mediums entspricht. Die mit dem Begriff der Strukturviskosität nach Ostwald verknüpften reversiblen und irreversiblen Vorgänge in plastischen Massen der vorstehend beschriebenen Art sind verantwortlich für die bei der Extrusion auftretenden Probleme.This very different behavior of the two masses indicates that the flow or deformation behavior corresponds to that of a so-called pseudoplastic medium. The reversible and irreversible processes in plastic masses of the type described above, which are associated with the concept of the structural viscosity according to Ostwald, are responsible for the problems which arise during extrusion.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren der eingangs genannten Art und eine Strangpresse der eingangs genannten Art zur Durchführung dieses Verfahrens zu schaffen, mit dem es möglich ist, durch einen Stangpreßprozeß formstabilisierte Grünkörper herzustellen aus Ausgangsmaterial für Glaskörper in Form einer relativ hochviskosen plastischen Preßmasse mit einem Feststoffanteil an hochdispersen Teilchen.The invention has for its object to provide a method of the type mentioned and an extruder of the type mentioned for performing this method, with which it is possible to produce shape-stabilized green body by an extrusion process from starting material for glass body in the form of a relatively highly viscous plastic molding compound with a solid fraction of highly disperse particles.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß die plastische Masse, die hochdisperses Si02-Pulver als Hauptbestandteil und Wasser als Dispergiermittel enthält, unter Ausnutzung des Thixotropieeffektes durch Einkopplung mechanischer Kräfte in einen Zustand erniedrigter Viskosität überführt und in diesem Zustand strangverpreßt wird.This object is achieved in that the plastic mass, which contains highly dispersed Si0 2 powder as the main constituent and water as the dispersant, is converted into a state of reduced viscosity by utilizing the thixotropy effect by coupling mechanical forces, and is extruded in this state.

Eine Strangpresse zur Durchführung dieses Verfahrens ist gekennzeichnet durch einen Preßstempel, mit dem ein Schall- oder Ultraschallfeld in eine zu verpressende thixotrope plastische Masse einkoppelbar ist, wobei der Preßstempel vorzugsweise aus einem Schwinger, einem über einen Haltering im Schwingungsknoten an den Schwinger angekoppelten Schwingungsverstärker und einer Sonotrode, über die das Ultraschallfeld in die zu verpressende plastische Masse einkoppelbar ist, besteht.An extrusion press for carrying out this method is characterized by a press ram with which a sound or ultrasound field can be coupled into a thixotropic plastic mass to be pressed, the press ram preferably comprising an oscillator, an oscillation amplifier coupled to the oscillator via a retaining ring in the oscillation node, and one Sonotrode, by means of which the ultrasonic field can be coupled into the plastic mass to be pressed.

Der Erfindung liegt die Erkenntnis zugrunde, daß der Thixotropieeffekt bei plastischen Massen mit hochdispersen Si02-Pulvern als Hauptbestandteil und H20 als Dispergiermittel dazu ausgenutzt werden kann, die plastische Masse zunächst durch Einwirkung mechanischer Kräfte, vorzugsweise Schall oder Ultraschall, in einem Zustand niedrigerer Viskosität zu überführen, wodurch ein Strangpreßprozeß möglich wird, der einen sehr viel niedrigeren Preßdruck erfordert, als wenn eine rheologisch nicht veränderte Masse zu verpressen wäre.The invention is based on the knowledge that the thixotropy effect in the case of plastic compositions with highly disperse Si0 2 powders as the main constituent and H 2 0 as the dispersant can be used to lower the plastic composition initially by the action of mechanical forces, preferably sound or ultrasound To transfer viscosity, which enables an extrusion process that requires a much lower pressure than if a rheologically unchanged mass were to be pressed.

Es wurde überraschend gefunden, daß hochgefüllte plastische Massen, deren Feststoffanteil überwiegend aus hochdispersen Si02-Teilchen besteht, praktisch unabhängig von ihrer Zusammensetzung, Vorbehandlung (Misch- und Homogenisierungsprozesse) und Dauer ihrer Lagerung (Exposition an Luft oder sonstiger Atmosphäre - Feuchtraum - ) in einen Zustand mit niedrigerer Viskosität und damit fast unbegrenzter Formbarkeit gebracht werden können, wenn diese Massen mit Schall oder Ultraschall behandelt werden. Dabei zeigte sich weiter, daß die Amplitude und damit die Energie der eingekoppelten Schallwellen die Ausbreitung der von der Sonotrode ausgehenden Erweichungsfront bestimmt. Für einen 1,5 kW-Ultraschallgenerator mit einer Grundfrequenz f = 20 kHz wurde experimentell gefunden, daß eine Verdopplung der Amplitude der Grundschwingung die Ausbreitungsgeschwindigkeit der Erweichungsfront um einen Faktor 3 bis 4 erhöht. Dieser Effekt kann dazu ausgenutzt werden, rohrförmige Körper durch Extrusion durch einen Ringspalt in geeignete Formen hinein oder stabförmige Körper durch Pressen der stark erweichten Massen durch Düsen in entsprechende Behälter hinein herzustellen.It was surprisingly found that highly filled plastic masses, the solids content of which consists predominantly of highly disperse Si0 2 particles, practically irrespective of their composition, pretreatment (mixing and homogenization processes) and duration of their storage (exposure to air or other atmosphere - damp room) in a state of lower viscosity and thus almost unlimited formability can be brought about if these materials are treated with sound or ultrasound. It was further shown that the amplitude and thus the energy of the coupled sound waves determine the spread of the softening front emanating from the sonotrode. For a 1.5 kW ultrasonic generator with a fundamental frequency f = 20 kHz, it was found experimentally that doubling the amplitude of the fundamental oscillation increases the rate of propagation of the softening front by a factor of 3 to 4. This effect can be used to produce tubular bodies by extrusion through an annular gap into suitable shapes or rod-shaped bodies by pressing the highly softened masses through nozzles into corresponding containers.

Nach vorteilhaften Weiterbildungen des Verfahrens nach der Erfindung wird als Ausgangsmaterial für den Glaskörper eine plastische Masse eingesetzt, die Si02-Partikel eines Durchmessers im Bereich von 10 bis 500 nm, vorzugsweise 15 bis 100 nm, mit einem mittleren Teilchendurchmesser von 40 nm enthält, wobei eine plastische Masse mit einem Feststoff:Wasser-Gewichtsverhältnis von 1:1,5 bis 1:1,8 eingesetzt wird. Hiermit ist der Vorteil verbunden, daß aus einem solchen Ausgangsmaterial trotz der relativ hohen Füllung mit hochdispersen Feststoffteilchen sehr homogene, hochverdichtete Grünkörper über einen Strangpreßprozeß hergestellt werden können.According to advantageous developments of the method according to the invention, a plastic mass is used as the starting material for the glass body, the SiO 2 particles with a diameter in the region from 10 to 500 nm, preferably 15 to 100 nm, with an average particle diameter of 40 nm, wherein a plastic mass with a solid: water weight ratio of 1: 1.5 to 1: 1.8 is used. This has the advantage that, despite such a relatively high filling with highly disperse solid particles, very homogeneous, highly compacted green bodies can be produced from such a starting material by means of an extrusion process.

Nach einer weiteren vorteilhaften Ausgestaltung des Verfahrens nach der Erfindung wird die plastische Masse durch Einkopplung eines Schallfeldes mit einer Frequenz f im Bereich von 20 bis 200 Hz oder durch Einkopplung eines Ultraschallfeldes mit einer Frequenz f im Bereich von 20 bis 50 kHz in einen Zustand erniedrigter Viskosität überführt. Eine Gel-Sol-Umwandlung tritt bei thixotropen Systemen bei jeder Art mechanischer Einwirkung, z.B. auch Rühren oder Schütteln, ein. Wird jedoch zur Verflüssigung einer hochviskosen Ausgangsmasse ein Schall- oder Ultraschallschwinger eingesetzt, dessen Amplitude so bemessen ist, daß das Schall- bzw. Ultraschallfeld in das zu verflüssigende Ausgangsmaterial eingekoppelt wird, ergibt sich eine besonders wirkungsvolle Auflösung von Packungshohlräumen im Ausgangsmaterial. Selbst solche Massen, die sich unter stetigem Druck auch bei Anwendung von Preßkräften in der Größenordnung von 3.104 N in üblichen Strangpreßverfahren nicht zu Strängen oder Rohren verpressen ließen, sondern sich völlig verfestigten, erfuhren bei Einwirkung von Schallenergie in praktisch allen Fällen eine mehr oder weniger starke Erweichung.According to a further advantageous embodiment of the method according to the invention, the plastic mass is brought into a state of reduced viscosity by coupling a sound field with a frequency f in the range from 20 to 200 Hz or by coupling in an ultrasound field with a frequency f in the range from 20 to 50 kHz transferred. A gel-sol conversion occurs in thixotropic systems with any type of mechanical action, such as stirring or shaking. However, if a sound or ultrasonic oscillator is used to liquefy a highly viscous starting mass, the amplitude of which is dimensioned such that the sound or ultrasonic field is coupled into the starting material to be liquefied, this results in a particularly effective dissolution of packing cavities in the starting material. Even such masses, which could not be pressed into strands or pipes under normal pressure even with the application of pressing forces of the order of 3.10 4 N in conventional extrusion processes, but were completely solidified, experienced more or less in practically all cases when exposed to sound energy strong softening.

Hierdurch kann erreicht werden, daß eine strukturviskose Masse mit einem relativ hohen Anteil an hochdispersen Feststoff-Teilchen mit relativ geringem Anpreßdruck in einer Strangpresse verformt werden kann, da sie infolge ihrer Thixotropie durch Einwirkung mechanischer Kräfte quasi schmierfettartige Konsistenz erlangt.In this way it can be achieved that a structurally viscous mass with a relatively high proportion of highly disperse solid particles with a relatively low contact pressure can be deformed in an extrusion press, since its thixotropy gives it a quasi grease-like consistency due to the action of mechanical forces.

Die mit der Erfindung erzielten Vorteile bestehen insbesondere darin, daß Grünkörper in einem kontinuierlichen Prozeß mit beliebigen Querschnittsformen und auch in großen Längen hergestellt werden können, daß die Herstellung eines Vielkomponentenglases möglich ist und daß die Herstellungseinrichtungen nicht besonders kostspielig sind.The advantages achieved by the invention consist in particular in that green bodies can be produced in a continuous process with any cross-sectional shapes and also in long lengths, that the production of a multi-component glass is possible and that the production facilities are not particularly expensive.

Anhand der Zeichnung werden Ausführungsbeispiele der Erfindung beschrieben und die Erfindung wird in ihrer Wirkungsweise erläutert.Exemplary embodiments of the invention are described with reference to the drawing and the mode of operation of the invention is explained.

Es zeigen

  • Fig. 1 Teil einer Strangpresse gemäß der Erfindung im Schnitt (Prinzipskizze)
  • Fig. 2a und 2d Schnittdarstellungen von Formen, in denen mittels der erfindungsgemäßen Strangpresse rohr- und stabförmige Grünkörper herstellbar sind.
Show it
  • 1 part of an extrusion press according to the invention in section (schematic diagram)
  • 2a and 2d sectional views of forms in which tubular and rod-shaped green bodies can be produced by means of the extrusion press according to the invention.

In Fig. 1 ist ein Teil einer Strangpresse mit einem Preßstempel 1 dargestellt. Der Preßstempel 1 ist aus mehreren Vorrichtungsteilen aufgebaut, nämlich aus einem im Ultraschallbereich bei einer Frequenz f von 20 kHz arbeitenden Schwinger 5, einem an einen, der Übertragung des Anpreßdrucks p dienenden Haltering 7 im Schwingungsknoten angekoppelten Schwingungsverstärker 9 und einer Sonotrode 11, über die das Ultraschallfeld in zu verpressende plastische Masse 3 einkoppelbar ist.In Fig. 1, a part of an extrusion press with a press ram 1 is shown. The press ram 1 is made up of several device parts, namely a vibrator 5 operating in the ultrasound range at a frequency f of 20 kHz, a holding ring 7 coupled to the transmission of the contact pressure p in the vibration node 9 and a sonotrode 11 via which the Ultrasonic field can be coupled into the plastic mass 3 to be pressed.

Der Schwinger 5 weist an seiner, dem Haltering 7 gegenüberliegenden Fläche ein Schwingungsdämpfungsteil auf, das aus einem Zwischenstück 17 aus piezoelektrischer Keramik und einem metallischen Reflektor 19 besteht. Die zu verpressende plastische Masse 3 befindet sich in einer Matrize 13, die eine Austrittsöffnung 15 aufweist. Der Preßstempel 1 mit seiner Sonotrode 11 ist in die Matrize 13 gleitfähig eng eingepaßt. Bei Vorschub des Stempels 1 unter einem Druck p tritt die plastische Masse 3 mit ihrem durch Einwirkung von Ultraschall in einen Zustand erniedrigter Viskosität überführten Anteil 33 über die Austrittsöffnung 15 in eine in einer Aufnahme 21 angeordnete zylindrische Form 23 (vergleiche Figuren 2a und 2b) ein.The oscillator 5 has on its surface opposite the retaining ring 7 a vibration damping part, which consists of an intermediate piece 17 made of piezoelectric ceramic and a metallic reflector 19. The plastic mass 3 to be pressed is located in a die 13 which has an outlet opening 15. The press die 1 with its sonotrode 11 is slidably fitted into the die 13. When the plunger 1 is advanced under a pressure p, the plastic mass 3, with its portion 33 converted into a state of reduced viscosity by the action of ultrasound, enters via the outlet opening 15 into a cylindrical shape 23 arranged in a receptacle 21 (see FIGS. 2a and 2b) .

In die Form 23 ist ein federnder zylindrischer Schwebekörper 25 gleitfähig eng eingepaßt, der auf einem Luftpolster L ruht und der sich bei Vorschub des Preßstempels 1 in Richtung auf eine Luftaustrittsöffnung 27 am unteren Ende der verschlossenen Form 23 verschiebt. Durch Regelung des Luftaustritts an der Luftaustrittsöffnung 27 läßt sich eine Gegenkraft in der Form 23 aufbauen, die eine Kompensation des Eigengewichtes der extrudierten Masse 33 ermöglicht und dadurch ein Arbreißen des geformten Preßlings in Form eines Vollzylinders verhindert. In Fig. 2b ist in der form 23 ein Kern 29 zentrisch angeordnet, der das Auspressen von rohrförmigen Grünkörpern ermöglicht. Für diesen Fall ist der Schwebekörper 25 hohlzylinderförmig ausgebildet und umschließt den Kern 29 gleitfähig eng.In the form 23, a resilient cylindrical float 25 is slidably fitted, which rests on an air cushion L and which, when the plunger 1 is advanced, moves in the direction of an air outlet opening 27 at the lower end of the closed form 23. By regulating the air outlet at the air outlet opening 27, a counterforce can be built up in the mold 23, which makes it possible to compensate for the weight of the extruded mass 33 and thereby prevents the molded compact from being torn in the form of a solid cylinder. In Fig. 2b, a core 29 is arranged centrally in the form 23, which enables the pressing of tubular green bodies. In this case, the float 25 is hollow-cylindrical and tightly encloses the core 29.

In den Figuren 2c und 2d ist eine Form 23 dargestellt, die die Herstellung langer Stäbe (Figur 2c) und langer Rohre (Figur 2d) ermöglicht. In dieser Anordnung ist die Sonotrode als Vollzylinder (Sonotrode 11) zur Herstellung von Rohren oder als Hohlzylinder (Sonotrode 31) zur Herstellung von Stäben ausgebildet.FIGS. 2c and 2d show a form 23 which enables the production of long bars (FIG. 2c) and long tubes (FIG. 2d). In this arrangement, the sonotrode is designed as a solid cylinder (sonotrode 11) for the production of tubes or as a hollow cylinder (sonotrode 31) for the production of rods.

Im Umfeld der Kontaktfläche der Sonotrode 11, 31 entsteht in der zu verpressenden Masse 3 ein Masseanteil 33, der eine gegenüber der Masse 3 erniedrigte Viskosität aufweist. Bei Vorschub der Sonotrode 11, 31 mit einer Vorschubgeschwindigkeit ö in Pfeilrichtung kann die niedrigerviskose Masse 33 in den Raum zwischen der Wandung der Form 23 und der Sonotrode 11 einströmen.In the vicinity of the contact surface of the sonotrode 11, 31, a mass fraction 33 is formed in the mass 3 to be pressed, which has a lower viscosity than the mass 3. When the sonotrode 11, 31 is fed at a feed speed δ in the direction of the arrow, the lower-viscosity mass 33 can flow into the space between the wall of the mold 23 and the sonotrode 11.

Wird, wie in Figur 2d dargestellt, eine als Hohlzylinder ausgebildete Sonotrode 31 eingesetzt, die gleitfähig eng in die Form 23 eingepaßt ist, kann die niedrigervoskose Masse 33 bei einer Vorschubgeschwindigkeit ö in Pfeilrichtung in den Innenraum der Sonotrode 31 einströmen und es wird ein stabförmiger Grünkörper erhalten. Die Form 23 wird zweckmäßigerweise aus lösbaren, abnehmbaren Rohrteilen zusammengesetzt, die nach Austreten des verformten Preßlings zur Verminderung der Wandreibung entfernt werden können.If, as shown in FIG. 2d, a sonotrode 31 designed as a hollow cylinder is used, which is slidably fitted into the mold 23, the lower-viscosity mass 33 can flow into the interior of the sonotrode 31 at a feed speed δ in the direction of the arrow and it becomes a rod-shaped ger preserved green body. The form 23 is expediently composed of detachable, removable tubular parts which can be removed after the deformed compact has emerged to reduce the wall friction.

In praktischen Ausführungsbeispielen wurden zu verpressende Massen hergestellt, wie sie in Tabelle I angegeben sind. Infolge unterschiedlicher Mischbehandlung und relativ langer Lagerung unter vermindertem Luftzutritt (bis zu 20 Tagen) zeigten die Massen eine sehr starke Verfestigung (hart, bröckelnd). Die Massen ließen sich in einer normalen Extrusionsanlage nicht extrudieren, sondern verfestigten sich noch stärker. Die dabei applizierten Kräfte bzw. Drücke am Düsenaustritt (Durchmesser des Düsenaustritts 1,6 cm) betrugen bis zu pmax = 30000 N (= p ≈ 1,5.108 Pa ≃ 1,5.103 bar). Die gleichen Massen wurden dann in der erfindungsgemäßen Strangpresse entsprechend Figur 1 einer Schallbehandlung unter folgenden Bedingungen unterzogen: eine Menge von etwa 50 cm3 der jeweiligen Masse wurde in den Füllraum der Matrize (Durchmesser 5 cm) etwa 3 cm hoch eingefüllt. Die Sonotrode eines Ultraschallgenerators für 20 kHz mit einer maximalen Schalleistung Ns = 1,5 kW (Wirkungsgrad 90%) wurde dann auf die Masse mit einem Anpreßdruck von p = 5.105 Pa $ 5 bar aufgesetzt. Die Schwingungsamplitude der Sonotrode wurde auf 7 µm eingestellt und die Masse unter diesen Bedingungen etwa 20 s lang beschallt. Die beschallte Masse erweichte in unmittelbarer Umgebung der Kontaktfläche am Sonotrodenboden zu schmierfettartiger Konsistenz. Unter dem Anpreßdruck p wanderte die Erweichungsfront in ca. 20 s, also mit einer mittleren Ausbreitungsgeschwindigkeit υ ≈ 1,5 mm/s durch die Füllmenge hindurch bis zur Austrittsöffnung an der Matrize; die Austrittsöffnung hatte einen Durchmesser von 8 mm; an der Austrittsöffnung trat eine Gesamtmenge an Masse mit erniedrigter Viskosität von ca. 1,5 cm3 in Form eines etwa 3 cm langen Stranges aus.In practical exemplary embodiments, masses to be pressed were produced, as indicated in Table I. Due to different mixing treatment and relatively long storage under reduced air access (up to 20 days), the masses showed a very strong solidification (hard, crumbling). The masses could not be extruded in a normal extrusion system, but solidified even more. The forces or pressures applied at the nozzle outlet (diameter of the nozzle outlet 1.6 cm) were up to pmax = 30000 N (= p ≈ 1.5.10 8 Pa ≃ 1.5.10 3 bar). The same masses were then subjected to a sound treatment in the extrusion press according to the invention in accordance with FIG. 1 under the following conditions: a quantity of approximately 50 cm 3 of the respective mass was introduced into the filling space of the die (diameter 5 cm) approximately 3 cm high. The sonotrode of an ultrasonic generator for 20 kHz with a maximum switching power N s = 1.5 kW (efficiency 90%) was then placed on the mass with a contact pressure of p = 5.10 5 Pa $ 5 bar. The oscillation amplitude of the sonotrode was set to 7 µm and the mass was sonicated for about 20 s under these conditions. The sonicated mass softened to a grease-like consistency in the immediate vicinity of the contact surface on the sonotrode base. Under the contact pressure p, the softening front migrated in about 20 s, i.e. with an average rate of propagation υ ≈ 1.5 mm / s through the filling quantity up to the outlet opening on the die; the outlet opening had a diameter of 8 mm; a total amount of mass with a reduced viscosity of approx. 1.5 cm3 emerged at the outlet opening in the form of an approximately 3 cm long strand.

In einem weiteren Ausführungsbeispiel wurde - unter Beibehaltung aller für das obige Beispiel genannten übrigen Parameter - die Schwingungsamplitude des Ultraschallgenerators auf 15 µm eingestellt. Unter diesen Bedingungen wanderte die Erweichungsfront in der zu verpressenden Masse nun mit einer Ausbreitungsgeschwindigkeit ? = 4 bis 6 mm/s durch die eingefüllte Masse, die praktisch quantitativ in der erwähnten schmierfettartigen Konsistenz durch die Austrittsöffnung der Matrize ausgepreßt wurde.In a further exemplary embodiment, the oscillation amplitude of the ultrasound generator was set to 15 μm while maintaining all the other parameters mentioned for the example above. Under these conditions did the softening front move in the mass to be pressed at a rate of expansion? = 4 to 6 mm / s through the filled-in mass, which was practically squeezed out quantitatively in the mentioned grease-like consistency through the outlet opening of the die.

Die auf die beschriebene Weise strangverpreßten Grünkörper wiesen eine Dichte von = 50 % der Dichte kompakten Quarzglases auf und waren porös, so daß nach ihrer Trocknung in einer nachfolgenden Reinigungspase in einer erhitzen Chlorgas enthaltenden Gasatmosphäre bei hoher Temperatur störende Verunreinigungen, insbesondere OH-Ionen und Ionen oder Teilchen der Übergangsmetalle weitgehend entfernt werden können. Der gereinigte Grünkörper wurde anschließend dichtgesintert. Der hergestellte Glaskörper hatte eine Dichte von 2,20 g/cm3 und war blasen- und schiierenfrei.The green bodies extruded in the manner described had a density of = 50% of the density of compact quartz glass and were porous, so that after drying in a subsequent cleaning phase in a gas atmosphere containing chlorine gas at high temperature, disturbing contaminants, in particular OH ions and ions or particles of the transition metals can be largely removed. The cleaned green body was then densely sintered. The glass body produced had a density of 2.20 g / cm 3 and was free of bubbles and streaks.

Gläser, die für optische Wellenleiter geeignet sind, sind ebenfalls mit Vorteil verwendbar für die Herstellung von Lampenkolben für Halogen- oder Gasentladungslampen, denn diese Gläser müssen, ebenso wie die Gläser für optische Wellenleiter, nahezu wasserfrei sein und einen hohen Siliciumdioxidgehalt aufweisen.Glasses which are suitable for optical waveguides can also be used with advantage for the production of lamp bulbs for halogen or gas discharge lamps, because these glasses, like the glasses for optical waveguides, must be virtually water-free and have a high silicon dioxide content.

BezugszeichenlisteReference symbol list

  • 1 Preßstempel1 press ram
  • 3 Plastische Masse3 Plastic mass
  • 5 Schwinger5 transducers
  • 7 Haltering7 retaining ring
  • 9 Schwingungsverstärker9 vibration amplifiers
  • 11 Sonotrode11 sonotrode
  • 13 Matrize13 die
  • 15 Austrittsöffnung15 outlet opening
  • 17 Zwischenstück17 intermediate piece
  • 19 Reflektor19 reflector
  • 21 Aufnahme für 2321 recording for 23
  • 23 Zylindrische Form23 Cylindrical shape
  • 25 Schwebekörper25 floats
  • 27 Luftaustrittsöffnung in 2327 air outlet opening in 23
  • 29 Kern in 2329 core in 23
  • 31 Hohlzylinderförmige Sonotrode31 Hollow cylindrical sonotrode
  • 33 Plastische Masse mit erniedrigter Viskosität33 Plastic mass with reduced viscosity

Claims (18)

1. Method for the manufacture of glass bodies, in which a porous green body is formed by extrusion from the starting material for the glass body in the form of a plastic mass and this green body is dried and subsequently purified and sintered, characterized in that the plastic mass, which comprises highly disperse Di02 powder as the main constituent and water as the dispersing agent, is transferred to a state of reduced viscosity utilizing the thixotropic effect and the action of mechanical forces, in which state said plastic mass is extruded.
2. Method as claimed in Claim 1, characterized in that the starting material for the glass body is a plastic mass which contains Si02 particles having a diameter in the range from 10 to 500 nm, preferably 15 to 100 nm, with an average particle diameter of 40 nm.
3. Method as claimed in Claim 1 or 2, characterized in that a plastic mass with a solids:water weight ratio of 1:1.5 to 1:1.8 is used.
4. Method as claimed in any one of the Claims 1 up to and including 3, characterized in that the plastic mass is transferred to a state of reduced viscosity by the introduction of a sound field with a frequency f in the range from 20 to 200 Hz or by the introduction of an ultrasound field with a frequency f in the range from 20 to 50 kHz.
5. Method as claimed in any one of the Claims 1 up to and including 4, characterized in that the plastic mass is extruded in an extruding press with a ram in the form of a sonotrode of a sonic or ultrasonic generator with a pressure p in the range from 1 to 7.105 Pa and an oscillation amplitude of the sonotrode in the range from 0 to 60 11m.
6. Extruding for the execution of the method as claimed in Claims 1 up to and including 5, comprising a cylinder having an outlet aperture and a ram which can move in said cylinder, characterized by a ram (1) which can be used to introduce a sound or ultrasound field into a thixotropic plastic mass (3, 33) to be extruded.
7. Extruding press as claimed in Claim 6, characterized in that the ram (1) consists of a resonator (5), an oscillation amplifier (9) coupled at the oscillation node to a supporting ring (7) which serves to transfer the pressure p and a sonotrode (11, 31) by means of which the ultrasound field can be introduced into the plastic mass (3, 33) to be extruded.
8. Extruding press as claimed in Claim 7, characterized in that on the surface lying opposite the supporting ring (7) the resonator (5) has an oscillation-damping unit comprising a spacer (17) of piezoelectric ceramic and a metallic reflector (19) by means of which the pressure p can be transferred to the ram (1).
9. Extruding press as claimed in any one of the Claims 6 up to and including 8, characterized in that the ram (1) with its sonotrode (11) is inserted with a sliding fit into a die (13) with an outlet aperture (15), and, when the ram advances under a pressure p, the mass to be extruded (3, 33) passes through the outlet aperture into a mould (23), corresponding to the shape of the glass body to be produced, arranged in a holder (21) below the outlet aperture.
10. Device as claimed in Claim 9, characterized in that a spring-mounted floating element (25) is provided in the mould (23).
11. Device as claimed in Claim 10, characterized in that the mould (23) is a hollow cylinder and the floating element (25) is cylindrical in shape and is inserted with a sliding fit into the mould (23).
12. Device as claimed in any one of the Claims 9 up to and including 11, characterized in that the mould (23) is a hollow cylinder and a centrally arranged core (29) is provided in the mould (23).
13. Device as claimed in Claim 12, characterized in that the floating element (25) is inserted into the mould (23) with a sliding fit and is in the shape of a hollow cylinder and encloses the core (29) with a sliding fit.
14. Device as claimed in any one of the Claims 9 up to and including 13, characterized in that the mould (23) is equipped with an air-outlet aperture (27) and its bottom end lying opposite the sonotrode (11).
15. Device as claimed in any one of Claims 6 up to and including 8, characterized in that a cylindrical closed mould (23) is provided which holds the plastic mass to be extruded (3, 33) and in which the ram (1) with its sonotrode (11) is fitted in such a way that, when the ram is advanced under a pressure p, a tube- shaped moulding emerges between the wall of the mould and the ram in the direction opposite to the direction of movement of the ram.
16. Device as claimed in Claim 15, characterized in that the ram (1) is provided with a sonotrode (31), in the form of a hollow cylinder, which is inserted into the mould (23) with a sliding fit, so that, when the ram is advanced under a pressure p, a rod-shaped moulding emerges via the inside of the sonotrode in the direction opposite to the direction of movement of the ram.
17. A method as claimed in Claims 1 up to and including 5, characterized in that the glass bodies manufactured are used as preforms for optical waveguides.
18. A method as claimed in Claims 1 up to and including 5, characterized in that the glass bodies manufactured are used as lamp envelopes, especially for halogen and gas discharge lamps.
EP86200488A 1985-03-29 1986-03-21 Process and devices for producing glass articles Expired - Lifetime EP0197586B1 (en)

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DE19853511452 DE3511452A1 (en) 1985-03-29 1985-03-29 METHOD AND DEVICES FOR THE PRODUCTION OF GLASS BODIES
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GB1010702A (en) * 1962-07-30 1965-11-24 Engelhard Ind Inc Quartz fibres and extruded rods
US3665064A (en) * 1967-01-05 1972-05-23 Nasa Method of making a perspiration resistant biopotential electrode
US3966381A (en) * 1973-11-21 1976-06-29 The Dow Chemical Company Extrusion of thermoplastic foam
DE2821642B2 (en) * 1977-05-24 1980-02-07 Hughes Aircraft Co., Culver City, Calif. (V.St.A.) Fiber optic waveguides and process for their manufacture
DE2903510C2 (en) * 1979-01-30 1981-06-25 Glacier Gmbh Deva Werke, 3570 Stadtallendorf Process and device for the continuous extrusion of electrically conductive granulated, preferably powder metallurgical materials
JPS59131538A (en) * 1983-01-18 1984-07-28 Seiko Epson Corp Production of quartz glass
JPS59152235A (en) * 1983-02-15 1984-08-30 Hitachi Cable Ltd Preparation of optical fiber
DE3314302A1 (en) * 1983-04-20 1984-10-25 Standard Elektrik Lorenz Ag, 7000 Stuttgart METHOD FOR PRODUCING POROUS GLASS BODIES, ESPECIALLY FOR THE PRODUCTION OF LIGHT-WAVE GUIDES
US4541855A (en) * 1983-08-18 1985-09-17 Corning Glass Works Method of forming a glass or ceramic product
JPS6054928A (en) * 1983-09-01 1985-03-29 Seiko Epson Corp Production of quartz glass
DE3563529D1 (en) * 1984-02-23 1988-08-04 Alcatel Nv Method of making a long glass body, particularly a preform for optical light guides

Also Published As

Publication number Publication date
US4685946A (en) 1987-08-11
EP0197586A2 (en) 1986-10-15
JPS61227934A (en) 1986-10-11
DE3511452A1 (en) 1986-10-09
CA1279289C (en) 1991-01-22
DE3671621D1 (en) 1990-07-05
EP0197586A3 (en) 1987-09-16

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